Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network™

Open Access. Powered by Scholars. Published by Universities.®

Physics

Institution
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 32251 - 32280 of 34093

Full-Text Articles in Entire DC Network

Γ8(3) Resonance In Esr Of (Ery)Al2 Single Crystals, U. Döbler, K. Baberschke, S. E. Barnes Jan 1983

Γ8(3) Resonance In Esr Of (Ery)Al2 Single Crystals, U. Döbler, K. Baberschke, S. E. Barnes

Physics Articles and Papers

Angle-dependent ESR results are given for 500-, 2500-, and 5000-ppm Er-doped YAl2 single crystals. An almost perfect analysis of the X- and Q-band data is achieved if the admixture of the first excited state Γ8(2) into the ground state Γ8(3) via the Zeeman interaction is taken into consideration. This enables us to determine the crystal electric field (CEF) parameter x=-0.322(20) and W=-0.29(2) K. The g-value shift yields N(EF)JΔg=+0.09(5) and the thermal broadening of the linewidth |N(EF)JΔH|=0.059(5). The precision of the experimental data allows, in principle, the determination …

Go to article

Gravity‐Induced Density And Concentration Profiles In Binary Mixtures Near Gas–Liquid Critical Lines, R. F. Chang, J. M. H. Levelt Sengers, T. Doiron, J. Jones Jan 1983

Gravity‐Induced Density And Concentration Profiles In Binary Mixtures Near Gas–Liquid Critical Lines, R. F. Chang, J. M. H. Levelt Sengers, T. Doiron, J. Jones

Physics Publications

We have calculated gravity‐induced density and concentration gradients using scaled equations of state fashioned after that of Leung and Griffiths for binary mixtures near gas–liquid critical lines. The mixtures considered here are those of helium‐3 and helium‐4 and of carbon dioxide and ethane. Our calculations show that the density profiles for both mixtures in any proportion of the components are similar to those of pure fluids. The concentration gradients in the helium mixture have the same appearance as the density gradients. In the carbon dioxide–ethane system, however, the form of the concentration profile varies greatly, depending on the overall composition. …

Go to article

Alternatives In Quantum Theory, Richard C. Heyser Jan 1983

Alternatives In Quantum Theory, Richard C. Heyser

Unpublished Writings

Quantum mechanical descriptions in terms of momentum and position are identified as alternatives under the condition of equal complex-vaulted Lebesgue square integrability. While this does not change any of the formal results obtained in quantum mechanics, it does shed a different interpretive light on the steps that lead up to these results. Instead of being independent, even in concept, momentum and position are identified as being the same thing, merely seen from different views. Neither is required to complement the descriptive capability of the other, since each forms a complete alternative in its own right. Apparent complementarity, as well as …

Go to article

Intermediate-Band Photometry Of Stars In Three Clusters Containing Classical Cepheids, Edward G. Schmidt Jan 1983

Intermediate-Band Photometry Of Stars In Three Clusters Containing Classical Cepheids, Edward G. Schmidt

Edward Schmidt Publications

Four-color and Hβ photometry has been carried out of stars in three sparse and distant clusters which are thought to contain Cepheids. From these data the distance moduli and color excesses of the clusters have been derived. In general the new values agree with those in the literature but are somewhat more precise.

Go to article

Interactive Computer Graphics: The Arms Race, David W. Hafemeister Jan 1983

Interactive Computer Graphics: The Arms Race, David W. Hafemeister

Physics

No abstract provided.

Go to article

A Chronology Of The Nuclear Arms Race, David W. Hafemeister Jan 1983

A Chronology Of The Nuclear Arms Race, David W. Hafemeister

Physics

No abstract provided.

Go to article

Comparison Of Model High-Latitude Electron Densities With Millstone Hill Observations, Jan Josef Sojka, Robert W. Schunk, J. V. Evans, J. M. Holt, R. H. Wand Jan 1983

Comparison Of Model High-Latitude Electron Densities With Millstone Hill Observations, Jan Josef Sojka, Robert W. Schunk, J. V. Evans, J. M. Holt, R. H. Wand

All Physics Faculty Publications

Model predictions of the diurnal variations of plasma convection velocities and electron densities in the high-latitude ionosphere were compared with Millstone Hill incoherent scatter radar observations for an equinox day on which there was moderate magnetic activity. On the observation day, three major morphological features were evident at 500 km, including a dayside high density region, a nightside mid-latitude trough, and a region of slightly enhanced densities in the auroral zone. Although the dayside high density region was due to solar EUV radiation, it was not symmetrical about local noon (1000-1900 LT sector) owing to the effect of horizontal transport. …

Go to article

Experimental Evidence For The Acceleration Of Thermal Electrons By Ion Cyclotron Waves In The Magnetosphere, A. J. Norris, J.F. E. Johnson, Jan Josef Sojka, G. L. Wrenn, N. Cornilleau-Wehrlin, S. Perraut, A. Roux Jan 1983

Experimental Evidence For The Acceleration Of Thermal Electrons By Ion Cyclotron Waves In The Magnetosphere, A. J. Norris, J.F. E. Johnson, Jan Josef Sojka, G. L. Wrenn, N. Cornilleau-Wehrlin, S. Perraut, A. Roux

All Physics Faculty Publications

Ion cyclotron waves (ICWs) at frequencies just above f He+ , the helium gyrofrequency, are often observed by the ESA satellites GEOS 1 and GEOS 2. Young et al. (1981) have shown the close connection between these ICWs and the presence of thermal He+ ions in the outer magnetosphere. The purpose of this paper is to provide experimental evidence for the acceleration of thermal electrons by the large amplitude ICWs. The wave power in the ultra low frequency (ULF) range near f He+ is compared with the distribution function of low energy electrons, measured by instruments aboard the GEOS satellites. …

Go to article

Comment On Coefficients Of Fractional Parentage Of The Form (L2L+1|}L2L+2), Anthony F. Starace Jan 1983

Comment On Coefficients Of Fractional Parentage Of The Form (L2L+1|}L2L+2), Anthony F. Starace

Anthony F. Starace Publications

For the special case of half-filled subshells, Racah showed in 1943 that his formula relating the coefficients of fractional parentage for a given particle configuration to those for the corresponding hole configuration requires an additional phase factor (-1) (v-1)/2, where v is the seniority of the half-filled configuration. This phase factor is incorrectly printed in Racah's 1943 paper as (-1) v-1/2. Furthermore, this phase factor is omitted in the 1952 paper by Rosenzweig, resulting in sign errors in the table of (d5|}d6) coefficients. These rather old errors have often …

Go to article

Thermal Propagation And Stability In Superconducting Films, Kenneth E. Gray, Robert T. Kampwirth, John F. Zasadzinski, Stephen P. Ducharme Jan 1983

Thermal Propagation And Stability In Superconducting Films, Kenneth E. Gray, Robert T. Kampwirth, John F. Zasadzinski, Stephen P. Ducharme

Stephen Ducharme Publications

Thermal propagation and stable hot spots (normal domains) are studied in various high Tc superconducting films (Nb3Sn, Nb, NbN and Nb3Ge). The prediction of the thermal propagation velocity of the long-standing model of Broom and Rhoderick (1960) is verified quantitatively in the regime of its validity. A new energy balance model is shown to give reasonable quantitative agreement of the dependence of the propagation velocity on the length of short normal domains. The steady state (zero velocity) measurements indicate the existence of two distinct situations for films on high thermal conductivity (sapphire) substrates. For low power per unit area the …

Go to article

Fluorescence Quenching At High Quencher Concentrations, David Peak, T C. Werner, R M. Dennin Jr., J K. Baird Jan 1983

Fluorescence Quenching At High Quencher Concentrations, David Peak, T C. Werner, R M. Dennin Jr., J K. Baird

All Physics Faculty Publications

Chemical reactions occurring in dense media at high reactant concentrations can be described by rate ‘‘constants’’ which are actually functions of concentration. We present a theoretical model in which this so‐called rate constant ‘‘renormalization’’ occurs for the specific case of fluorescence quenching in solution. We show that both the quenching and the excitation rate constants can become concentration dependent. We fit our theory to several sets of experimental data—our own and some from the literature—and show that excellent agreement is obtained by varying a single free parameter, namely, the efficiency with which a fluorophore‐quencher collision leads to a quench of …

Go to article

Incoherent Scatter Measurements Of Ion-Neutral Collision Frequencies And Temperatures In The Lower Thermosphere Of The Auroral Region, C. Lathuillere, Vincent B. Wickwar, W. Kofman Jan 1983

Incoherent Scatter Measurements Of Ion-Neutral Collision Frequencies And Temperatures In The Lower Thermosphere Of The Auroral Region, C. Lathuillere, Vincent B. Wickwar, W. Kofman

All Physics Faculty Publications

Incoherent scatter observations performed in March and November 1978 at Chatanika have been used for studying the lower thermosphere in the auroral region. Neutral temperatures and densities have been found during periods without Joule heating. We present mean profiles of temperatures and collision frequencies (approximately proportional to neutral densities) for each month and profiles obtained during four specific nights. Between 93 km and 110 km the mean profiles of temperature are in good agreement with the Jacchia (1971) model, and the profiles of collision frequency are similar to those deduced from the model. Consistency checks between these collision frequencies and …

Go to article

Large-Scale Counterstreaming Of H+ And He+ Along Plasmaspheric Flux Tubes, P. G. Richards, Robert W. Schunk, Jan Josef Sojka Jan 1983

Large-Scale Counterstreaming Of H+ And He+ Along Plasmaspheric Flux Tubes, P. G. Richards, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

An interhemispheric plasma transport model has been used to study the flow characteristics of H+, He+, and O+ along closed geomagnetic field lines for solstice conditions at noon local time. The calculations were carried out for the flux tube that passes through Millstone Hill. Both symmetric and asymmetric neutral winds in the conjugate ionospheres were considered. Initially, the flux tube content was partially depleted, and the subsequent refilling was studied until a steady state flow was established between the winter and summer hemispheres. The main conclusion to be drawn from this study is that H+-He+ counterstreaming can be expected along …

Go to article

A Theoretical Study Of The High Latitude F Region’S Response To Magnetospheric Storm Inputs, Jan Josef Sojka, Robert W. Schunk Jan 1983

A Theoretical Study Of The High Latitude F Region’S Response To Magnetospheric Storm Inputs, Jan Josef Sojka, Robert W. Schunk

All Physics Faculty Publications

The response of the polar ionosphere to magnetospheric storm inputs was modeled. During the storm the two major processes that couple the F region to the magnetosphere, namely the electric field distribution and the particle precipitation from the magnetosphere, undergo drastic modification on relatively short F region time scales. These time-dependent changes are not simply related to the F region storm time dependent changes. The lower F region responds on a time scale of only minutes to the storm associated changes in the auroral precipitating electron flux, owing to the dominance of chemistry production-loss mechanisms over transport processes. At higher …

Go to article

Preliminary Rovibrational Analysis Of The Nν6+Ν1−Nν6 Vibration In Hcn⋅⋅⋅Hf, E. Kyrö, K. Mcmillan, M. Eliades, D. Danzeiser, P. Shoja-Chaghervand, Shannon Lieb, J. W. Bevan Jan 1983

Preliminary Rovibrational Analysis Of The Nν6+Ν1−Nν6 Vibration In Hcn⋅⋅⋅Hf, E. Kyrö, K. Mcmillan, M. Eliades, D. Danzeiser, P. Shoja-Chaghervand, Shannon Lieb, J. W. Bevan

Scholarship and Professional Work - LAS

A preliminary rotation‐vibration analysis of the n=0 and n=1 subbands associated with the nν6+ν1−nν6 hydrogen‐bonded vibration in HCN⋅⋅⋅HF has been completed. The following excited staterotational constantsB′ and band origin frequencies ν0 have been determined for the complex. The results are consistent with a rotation‐vibration interaction constant α1=−68.3±1 MHz which correlates with an excited stater(N⋅⋅⋅F) internuclear distance of 2.762 Å, a decrease of 0.034 Å relative to the ground state.Excited state lifetimes associated with assigned transitions are demonstrated to be …

Go to article

Characteristics Of Thermal And Suprathermal Ions Associated With The Dayside Plasma Trough As Measured By The Dynamics Explorer Retarding Ion Mass Spectrometer, Jan Josef Sojka, Robert W. Schunk, J.F. E. Johnson, J. H. Waite, C. R. Chappell Jan 1983

Characteristics Of Thermal And Suprathermal Ions Associated With The Dayside Plasma Trough As Measured By The Dynamics Explorer Retarding Ion Mass Spectrometer, Jan Josef Sojka, Robert W. Schunk, J.F. E. Johnson, J. H. Waite, C. R. Chappell

All Physics Faculty Publications

The retarding ion mass spectrometer (RIMS) instrument on Dynamics Explorer 1 has carried out high-altitude measurements of the polar wind. During an outbound pass through the outer plasmasphere and plasma trough at 0900 LT the RIMS instrument measured the detailed characteristics of the thermal and suprathermal ions. Three distinct populations were observed: (1) thermal ions (H+ and He+) with densities ranging from > 500 ions/cm3 to < 1 ion/cm3, temperatures around 2 eV (20,000° K), and H+/He+ density ratios of 2 to 4, (2) warm anisotropic plasma with densities ranging from 2 to 12 ions/cm …

Go to article

Preferential Perpendicular Acceleration Of Heavy Ionospheric Ions By Interactions With Electrostatic Hydrogen Cyclotron Waves, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka Jan 1983

Preferential Perpendicular Acceleration Of Heavy Ionospheric Ions By Interactions With Electrostatic Hydrogen Cyclotron Waves, Nagendra Singh, Robert W. Schunk, Jan Josef Sojka

All Physics Faculty Publications

The energization of heavy ionospheric ions by electrostatic hydrogen cyclotron (EHC) waves is examined. In particular, the problem of preferential perpendicular acceleration of heavy ions above 5000 km along auroral field lines is examined critically. Observations have indicated that above this altitude the occurrences of ion beams and EHC waves are highly correlated and that the occurrence rates are high. The EHC waves are found to be coherent. The energization process is examined in the light of interactions of a single coherent wave with the ions. The interactions can be stochastic or nonstochastic, depending on the parameters of the wave …

Go to article

Physics, Robert B. Witmer, Wilbur O. Weisser Jan 1983

Physics, Robert B. Witmer, Wilbur O. Weisser

UND Departmental Histories

This departmental history was written on the occasion of the UND Centennial in 1983.

Go to article

Seam Wave Characteristics In An Eastern U.S. Coal, Paul J. Wolfe, Timothy G. Holdeman, Benjamin H. Richard Jan 1983

Seam Wave Characteristics In An Eastern U.S. Coal, Paul J. Wolfe, Timothy G. Holdeman, Benjamin H. Richard

Physics Faculty Publications

No abstract provided.

Go to article

Nitrogen Escape From Mars, Jane L. Fox, Alexander Dalgarno Jan 1983

Nitrogen Escape From Mars, Jane L. Fox, Alexander Dalgarno

Physics Faculty Publications

The escape rate of nitrogen from Mars is calculated to be 2.3×105 s−1 for low solar flux conditions and 8.9×105 s−1 for high solar flux conditions. The major source of energetic atoms is dissociative recombination of ground state and vibrationally excited N2+ ions. The measured 15N/14N isotope ratio can be reproduced by postulating an early dense atmosphere during which little differentiation occurred.

Go to article

Stopping Power Of K Electrons At Extreme Relativistic Energies, P.T. Leung, M. L. Rustgi Jan 1983

Stopping Power Of K Electrons At Extreme Relativistic Energies, P.T. Leung, M. L. Rustgi

Physics Faculty Publications and Presentations

The recent work of Anholt (1979) on K-vacancy production by relativistic projectiles has been applied to calculate the stopping power of the K electrons. The results show that for protons of energy ~10³ GeV and heavy target elements, the relativistic contributions to the stopping power amount to several times the results due to the longitudinal terms obtained from Walske's (1956) work.

Go to article

Intermolecular Interactions For Phosphatidyl Choline And Phosphatidyl Ethanolamine, Tony Flaim, Stig Friberg, Patricia L.M. Plummer Jan 1983

Intermolecular Interactions For Phosphatidyl Choline And Phosphatidyl Ethanolamine, Tony Flaim, Stig Friberg, Patricia L.M. Plummer

Chemistry Faculty Research & Creative Works

Intermolecular interaction between pairs of methylphosphocholine (MPC) and methylphosphoethanolamine were calculated using an extended CNDO/2 program. Experimentally determined conformations were used for the ethanolamine and choline groups. In the methylphosphocholine the major interaction was intramolecular, involving the phosphate ester-choline groups, while in the ethanolamine the maximum attraction was intermolecular between the ethanolamine and the phophate ester of a neighboring molecule(s). © 1983.

Go to article

A General Nmr Spectral Density And Its Experimental Verification, A. M. Albano, Peter A. Beckmann, M. E. Carrington, F. A. Fusco, A. E. O'Neill, M. E. Scott Jan 1983

A General Nmr Spectral Density And Its Experimental Verification, A. M. Albano, Peter A. Beckmann, M. E. Carrington, F. A. Fusco, A. E. O'Neill, M. E. Scott

Physics Faculty Research and Scholarship

The authors develop a new general spectral density for use in interpreting nuclear spin-lattice relaxation measurements in molecular solids where molecular and/or intramolecular reorientation is responsible for the relaxation. They show that the simplest case of the general theory fits both the temperature and Lamor frequency dependence of some very complicated relaxation measurements which could not be previously fitted using several standard spectral densities. The relationship of the spectral density to a distribution of molecular potentials is briefly outlined.

Go to article

On The Schrödinger Spin‐Exchange Ferromagnet, Harry A. Brown Jan 1983

On The Schrödinger Spin‐Exchange Ferromagnet, Harry A. Brown

Physics Faculty Research & Creative Works

The thermodynamic behavior of a ferromagnet whose interactions are described by the Schrödinger spin‐exchange operator is investigated. The transition temperatures, magnetization, susceptibility, exchange energy, heat capacity, and entropy are calculated for general spin and lattice coordination number using the constant‐coupling approximation. Both first‐ and second‐order phase transitions are found. Comparison with some results of the high‐temperature expansion method shows some qualitative agreement. Copyright © 1983 WILEY‐VCH Verlag GmbH & Co. KGaA

Go to article

Application Of The Impact Approximation To Collisional Line Shifts In Na-Rare Gas Systems, Mahdi Azougui Jan 1983

Application Of The Impact Approximation To Collisional Line Shifts In Na-Rare Gas Systems, Mahdi Azougui

Masters Theses

"This dissertation deals, mainly, with the line shifts of the excited atoms of sodium induced by collisions with argon atoms. The general work is based on the study of both, broadenings of the lines and line shifts with a particular emphasis on the latter. A review is given for the case of very large principal quantum numbers N; then the binary collision method is detailed for low transitions (N ≤ 6) where the computed values are in very good agreement with the experimental results obtained by Krebs and Schearer.1 This method breaks down at larger N. Next, a modification …

Go to article

Are There Any Shock-Heated Galaxies?, Gary J. Ferland, Hagai Netzer Jan 1983

Are There Any Shock-Heated Galaxies?, Gary J. Ferland, Hagai Netzer

Physics and Astronomy Faculty Publications

We study the spectroscopic characteristics of low ionization nuclear emission-line regions (Liners) in galaxies, and compare them with other active galactic nuclei. We show the results of new, extensive photoionization model calculations and use them to investigate line ratio diagrams, such as [O III] λ5007/Hβ versus [O II] λ3727/[O III] λ5007, and [O I] λ6300/[O III] λ5007 versus [O III] λ3727/[O III] λ5007. On the diagrams broad line objects, Seyfert 2 galaxies, and Liners form a continuous smooth sequence of decreasing ionization parameter. This suggests a common origin for line excitation in …

Go to article

Linear Inversion Method To Obtain Aerosol Size Distributions From Measurements With A Differential Mobility Analyzer, Donald E. Hagen, Darryl J. Alofs Jan 1983

Linear Inversion Method To Obtain Aerosol Size Distributions From Measurements With A Differential Mobility Analyzer, Donald E. Hagen, Darryl J. Alofs

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Use of a Differential Mobility Analyzer to Perform Aerosol Size Spectrum Measurements Requires an Inversion Method to Go from the Measured Sensor Responses to the Desired Size Spectrum Information. Here We Present a Linear Inversion Method that Can Be Run on a Microcomputer or a Small Minicomputer. It Does Not Use Some of the Approximations Made in the Techniques Currently Available and Hence Gives Better Inversion Accuracy. the Method Shows Good Immunity to Both Random and Systematic Experimental Error. It is Applied to Numerous Test Case Aerosols. © 1983 Elsevier Science Publishing Co., Inc.

Go to article

Universal Stationary-Phase Treatment Of Far-Wing And Excimer Spectral Line Shapes, Ronald James Bieniek, T. J. Streeter Jan 1983

Universal Stationary-Phase Treatment Of Far-Wing And Excimer Spectral Line Shapes, Ronald James Bieniek, T. J. Streeter

Physics Faculty Research & Creative Works

When two atoms are in proximity, their resonance lines are broadened because of the formation of molecular potentials, between which photon transitions can occur. The level of experimental refinement in measuring excimer and collisional far-wing spectra calls for interpretive theoretical methods that accurately treat the observed structure in line shapes. Of particular interest are satellites and undulations, for they can give much information on intermolecular potentials. We derive an expression for T-matrix elements, based on JWKB wave functions and stationary-phase techniques, that is universally applicable to situations with one, two, or more Condon points. Each transition point is treated individually, …

Go to article

Nanosecond Optical Transmission Studies Of Laser Annealing In Ion-Implanted Silicon-On-Sapphire, M. C. Lee, H. W. Lo, A. Aydinli, G. J. Trott, A. Compaan, Edward Boyd Hale Jan 1983

Nanosecond Optical Transmission Studies Of Laser Annealing In Ion-Implanted Silicon-On-Sapphire, M. C. Lee, H. W. Lo, A. Aydinli, G. J. Trott, A. Compaan, Edward Boyd Hale

Physics Faculty Research & Creative Works

Time-resolved optical transmission has been studied using 633 and 514 nm CW probes on ion-implantation-amorphized silicon-on-sapphire during annealing by a 10 nsec, ⊥ J/cm2 pulse at either 532 nm or 485 nm. As recrystallization sets in the transmitted signal at 514 nm rises by ⊥ 103 in ⊥ 60 nsec and provides a measure of regrowth velocity. Beyond 200 nsec the much slower transmission rise is used to provide an estimate of the Si cooling rate. The difference in transmission observed between initially crystalline and initially amorphous Si provide an estimate of the latent heat of recrystallization of the amorphous …

Go to article

Collisions Of Fast Highly Charged Ions In Gas Targets: Ionization, Recoil-Ion Production, And Charge Transfer, A. S. Schlachter, K. H. Berkner, H. F. Beyer, W. G. Graham, W. Groh, R. Mann, A. Müller, Ronald E. Olson, R. V. Pyle, J. W. Stearns, J. A. Tanis Jan 1983

Collisions Of Fast Highly Charged Ions In Gas Targets: Ionization, Recoil-Ion Production, And Charge Transfer, A. S. Schlachter, K. H. Berkner, H. F. Beyer, W. G. Graham, W. Groh, R. Mann, A. Müller, Ronald E. Olson, R. V. Pyle, J. W. Stearns, J. A. Tanis

Physics Faculty Research & Creative Works

Electron-capture, ionization, and recoil-ion-production cross-sections are measured and calculated for fast highly charged projectiles in hydrogen and rare-gas targets. Recoil-ion-production cross-sections are found to be large; the low energy and high charge states of the recoil ions make them useful for subsequent collision studies. © 1983 IOP Publishing Ltd.

Go to article

First Prev Next Last